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Ache P, Bauer H, Kollist H, Al-Rasheid KA, Lautner S, Hartung W, Hedrich R: Stomatal action directly feeds back on leaf turgor: New insights into the regulation of the plant water status from non-invasive pressure probe measurements. Plant J. 2010 Mar 25.
SUMMARY Uptake of CO (2) by the leaf is associated with loss of water. Control of stomatal aperture by volume changes of guard cell pairs optimizes the water-use-efficiency. Under water stress the protein kinase OST1 activates the guard cell anion release channel SLAC1 and thereby triggers stomatal closure. Plants with mutated OST1 and SLAC1 are defective in guard cell turgor regulation. To study the effect of stomatal movement on leaf turgor with intact leaves of Arabidopsis, we used a new pressure probe to monitor simultaneously and non-invasively transpiration and turgor pressure. This probe permits routinely and easy access of parameters related to the water status and stomatal conductance under physiological conditions with the model plant Arabidopsis thaliana. Long term leaf turgor pressure recordings over several weeks showed a drop in turgor during the day and recovery at night. Thereby pressure changes directly followed the degree of plant transpiration. Leaf turgor of wild type plants responded to CO (2), light, humidity, ozone and abscisic acid (ABA) in a guard cell-specific manner. In pressure probe measurements mutants lacking OST1 and SLAC1 function appeared impaired in their stomatal responses to light and humidity. In contrast to wild type plants, leaves from well-watered ost1 plants exposed to a dry atmosphere wilted immediately following light-induced stomatal opening. Experiments with open-stomata-mutants indicated that the hydraulic conductance of leaf stomata is higher than that of the root-shoot-continuum. Leaf turgor to a large extent thus seems to rely on the anion channel activity of autonomously regulated stomatal guard cells. |
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